1. Bred from eggs laid by a female of the winter form on 12th-15th
May, 1868, in a breeding-cage. The caterpillars emerged on 20th-22nd
May, and pupated on 7th-9th June. The pupæ, kept at the ordinary
temperature, produced:--
On the 19th of June 4 butterflies.
” 20th ” 5 ”
” 21st ” 10 ”
” 22nd ” 9 ”
” 23rd ” 7 ”
” 25th ” 13 ”
--
Total 48 ”
All these butterflies were of the _Prorsa_ type, 3 females having a
considerable amount of yellow, but none with so much as figs. 3, 4, 7,
8, or 9. Pl. I.
2. August 12th, 1868, found larvæ of the third generation, which
pupated at the beginning of September, and were kept in a room not
warmed. In September three butterflies emerged in the _Prorsa_ form,
the remainder hibernating and producing, after being placed in a heated
room at the end of February, from the 1st to the 17th of March, 1869,
more butterflies, all of the _Levana_ form.
3. Larvæ found on the 17th June, 1869, were sorted according to colour;
the yellow ones, with light brown spines, produced, at the ordinary
temperature, on 8th-12th July, 13 butterflies, 12 of which showed the
ordinary _Prorsa_ type, and one, a male, possessing more yellow than
fig. 3, Pl. I., must be considered as a _Porima_ type.
4. From caterpillars of the second generation, found at the same
time as those of Exp. 3, 30 pupæ were placed in the refrigerator
(temperature 8°-10° R.) on June 25th. When the box was opened on
August 3rd, almost all had emerged, many being dead, and all, without
exception, were of the intermediate form (_Porima_), although nearer
the _Prorsa_ than the _Levana_ type.
5. A large number of caterpillars of the second generation, found at
the same time, pupated, and were kept at a high summer temperature.
After a pupal period of about 19 days, some 70 butterflies emerged from
28th June to 5th July, all of the _Prorsa_ form, with the exception of
5, which were strongly marked with yellow (_Porima_).
6. The 70 butterflies of the foregoing experiment were placed in an
enclosure 6 feet high, and 8 feet long, in which, during warm weather,
they freely swarmed on flowers. Copulation was only once observed, and
but one female laid eggs on nettle on July 4th. At the high summer
temperature prevailing at the time, these eggs produced butterflies
after 30-31 days (third generation). All were _Prorsa_, with more or
less yellow; among 18 none were completely _Porima_.
7. Young larvæ of the fourth generation, found on the 8th of August,
were reared in a hothouse (17°-20° R.). They pupated on 21st-23rd
August. Of these:--
A. 56 pupæ were placed on ice (0°-1° R.) for five weeks, and then
allowed to hibernate in a room not warmed. In April, 1870, they all
gave the _Levana_ form, with the exception of a single _Porima_.
B. About an equal number of pupæ were placed in the hothouse, but
without any result; for, notwithstanding a temperature of 12°-24° R.,
not a single butterfly emerged in the course of October and November.
The pupæ were then allowed to hibernate in an unheated room, and in
April and May gave nothing but _Levana_.
8. Caterpillars of the second generation, found at the beginning of
June, 1870, pupated on 13th-15th June, and gave, at the ordinary
temperature, on June 29th-30th, 7 butterflies of the _Prorsa_ form.
9. Pupæ of the same (second) generation were placed immediately after
pupation on June 18th, 1870, in a refrigerator (0°-1° R.), and after
remaining there four weeks (till July 18th) gave, at the ordinary
summer temperature:--
On the 22nd of July, 2 _Prorsa_.
” 23rd ” 3 ”
” 24th ” 6 _Porima_, 4 of which were
very similar to _Levana_.
” 25th ” 1 _Levana_, without the blue
marginal line.
” 26th ” 2 _Levana_, also without the
blue marginal line.
” 2nd August, 6 _Porima_.
--
Total 20
Of these 20 butterflies only 5 were of the pure _Prorsa_ form.
10. Full grown larvæ of the fourth generation, found on August 20th,
1870, pupated on August 26th to September 5th. The pupæ were divided
into three portions:--
A. Placed in the hothouse (12°-25° R.), immediately after pupation and
left there till October 20th. Of about 40 pupæ only 4 emerged, 3 of
which were _Prorsa_ and 1 _Porima_. The remaining pupæ hibernated and
all changed into _Levana_ the following spring.
B. Kept in a room heated to 6°-15° R. from November. Not a single
specimen emerged the same year. This lot of pupæ were added to C from
November.
C. Placed on ice for a month immediately after pupation; then,
from September 28th to October 19th in the hothouse, where no more
butterflies emerged. The pupæ hibernated, together with those from lot
B, in a room heated by water to 6°-15° R., and gave:--
On the 6th of February, 1 female _Levana_.
” 22nd ” 1 male _Levana_.
” 23rd ” 1 male _Levana_.
” 24th ” 1 female _Levana_.
” 25th ” 1 male and 1 female _Levana_.
” 28th ” 1 male and 1 female _Levana_.
” 1st of March, 1 male _Levana_.
” 13th ” 1 female _Levana_.
” 15th ” 1 female _Levana_.
” 19th ” 1 male _Levana_.
” 2nd of April, 2 male and 1 female _Levana_.
” 7th ” 1 female _Levana_.
” 21st ” 1 female _Levana_.
” 2nd of May, 1 female _Levana_.
--
Total 18 _Levana_, 10 of which were females.
The exact record of the time of emergence is interesting, because it is
thereby rendered apparent that different individuals respond more in
different degrees to a higher than to the ordinary temperature. Whilst
with many an acceleration of development of 1-2 months occurred, others
emerged in April and May, i.e. at the time of their appearance in the
natural state.
11. Reared the second generation from eggs of the first generation.
Emerged from the eggs on June 6th, 1872, pupated on July 9th. The pupæ
were placed on ice (0°-1° R.) from July 11th till September 11th, and
then transferred to a hothouse, where all emerged:--
On the 19th of September, 3 male _Prorsa_, 1 male _Porima_.
” 21st ” 13 _Porima_ (12 males, 1 female),
2 female _Levana_.
” 22nd ” 14 _Porima_ (12 males, 2 females)
and 1 female _Levana_.
” 23rd ” 10 female _Levana_, 3 male _Porima_.
” 24th ” 5 female _Levana_.
” 25th ” 1 female _Levana_.
” 27th ” 3 female _Levana_.
” 4th of October, 1 male _Porima_.
--
Total 57 butterflies (32 males and 25 females),
only 3 of which were _Prorsa_, 32 _Porima_, and 22 _Levana_.
It must be pointed out, however, that among those specimens marked
as “_Levana_” there were none which entirely corresponded with the
natural _Levana_, or which indeed approximated so nearly to this form
as did some of the specimens in Exp. 9. All were larger than the
natural _Levana_, and possessed, notwithstanding the large amount of
yellow, more black than any true _Levana_. In all artificially bred
_Levana_ the black band of the basal half of the hind wings is always
interrupted with yellow, which is seldom the case with true _Levana_.
The whole appearance of the artificial _Levana_ is also coarser, and
the contour of the wings somewhat different, the fore-wings being
broader and less pointed. (See figs. 7 to 9, Pl. I.).
12. Larvæ of the fourth generation, found on September 22nd, 1872, were
divided into two portions:--
A. Placed for pupation in an orchid-house at 12°-25° R., and allowed
to remain there till December. In spite of the high temperature not
a single butterfly emerged during this time, whilst pupæ of _Vanessa
C-album_ and _Pyrameis Atalanta_, found at the same time, and placed in
the same hothouse, emerged in the middle of October. From the middle of
December the pupæ were kept in an unheated room, and they emerged very
late in the spring of 1873, all as _Levana_:--
On the 6th of June, 7 _Levana_.
” 8th ” 2 ”
” 11th ” 2 ”
” 12th ” 1 ”
” 15th ” 6 ”
” 16th ” 1 ”
” 19th ” 2 ”
--
Total 21 ”
B. Kept in an unheated room during the winter. The butterflies emerged
from the 28th of May, all as _Levana_.